50 horse merc alarm horn

[overdalimit]

My in-laws just bought a pontoon with a 1997 50 hp merc 4 stroke. Runs good but the alarm horn will sound at an idle hot or cold doesn't matter. Oh yeah not all the time either ha ha. It is a steady tone that lasts about a minute then shuts off. When the horn is sounding the motor won't rev up. I assume this is to protect the motor, as soon as horn stops the motor runs fine. Anybody having an ah-ha moment? The boat was delivered with a borrowed trailer so we are going to try and figure this out ourselves if we can...we are looking for an 18 ft toon trailer too so if anybody knows of one...

[ducker]

You probably have already done it but check the oil level.

[Northlander]

That was my 1st guess as well.

[boatfixer]

A steady tone on a merc of that vintage is related to the over heat warning.

You say cold or hot??

The first thing I would try is to disconnect the tan wire from the sender located on the back or aft end of the block near the top. if the tone quits, its the sender. If the tone continues, its possible the warning module is malfuntioning.

I also will read the temp with my lazer thermometer just to verify temp.

[bassNspear]

i was going to say over heat or oil. might have to replace the water pump

[Valv]

..we are looking for an 18 ft toon trailer too so if anybody knows of one...

If you need to take boat to a lake, you can always rent one of these "scissor" type trailers, usually dealers ask around $ 50/day.

But BEWARE to go VERY, VERY, VERY, VERY slow on turns and take offs while turning or you will flip your boat over very quickly, these trailers are nasty.

[bassNspear]

ya, they get out of control sometimes!

[overdalimit]

So far it has had the plugs replaced and the water pump changed but alarm still sounds at an idle once in a while. I have not had time to try pulling the tan wire off of the sensor while it is running but perhaps next weekend to isolate the temp sensor.

[harvey lee]

The temp sensor would be a good one to check out. MIne went out and did the same thing.

The other issue I had was there were a couple small pebbles in my thermostat and it would let a small amount of water into the crankcase and set an alarm.

Its an easy thing to check.